Breastfed babies cope better with stress later in life, according to new research.

A study of almost 9,000 British children found those weaned naturally suffered less anxiety as they grew older than those reared on the bottle with formula milk.

Previous research has shown mother's milk staves off a number of health problems for their young including heart disease.

The Swedish analysis found bottle fed children were over four times as likely to be highly stressed by difficult life events than their breastfed peers.

Their findings published online by the Archives of Disease in Childhood are based on children who were part of the 1970 British Cohort Study which regularly monitors a sample of the population from birth onwards.

Relevant information was obtained at the children's birth and at the ages of five and ten from midwives, health visitors, parents, and teachers. This included how much the children weighed at birth and whether they were breastfed.

When the children were 10-years-old their teachers were also asked to rate the anxiety of their pupils on a scale of zero to 50 while parents were interviewed about major family disruption - including divorce or separation - which had occurred when their child was between five and 10.

Unsurprisingly when all the data were analysed the findings pointed to a greater likelihood of high anxiety among children whose parents had divorced or separated.

But children who had been breastfed were significantly less anxious than their peers who had been bottle-fed.

Breastfed children were almost twice as likely to be highly anxious - while children who had been bottle fed were over nine times as likely to be highly anxious about parental divorce or separation.

The findings held true irrespective of other factors likely to influence the results.

Epidemiologist Dr Scott Montgomery, of the Karolinska Institute, Stockholm, said: "The analysis found parental divorce and separation were associated with a greater anxiety among children who were not breast fed than among breast fed children."

The researchers said the study does not prove breastfeeding itself makes children cope better with life stress - instead it could be a marker of some other maternal or parental factors.

But they cite animal research which suggests the quality of physical contact between mother and baby during the first few days of life may influence the development of the offspring's neural and hormonal pathways involved in the stress response.

Babies with more of the type of contact experienced during breast feeding coped better with stress when older.

Breastfeeding could also affect the quality of the bonding between mother and child and the way in which the two relate to each other.

And this could have a lasting impact on the child's anxiety levels in response to stressful life events.

Dr Montgomery said: "Breast feeding is associated with resilience against the psychosocial stress linked with
parental divorce or separation.

"This could be because breast feeding is a marker of exposures related to maternal characteristics and parent–child interaction.

"The benefits of breast feeding are well recognised and this study indicates it may be associated with lower levels of anxiety among children who have had the potentially stressful experience of parental divorce."